1. Field of the Invention
The present invention relates to an apparatus for exposing an optical disc master plate, and in particular, to an exposing apparatus for exposing an optical disk master plate which exposes a photoresist master plate and writes in a DVD-R (Digital Video Disc Recordable) format therein, and a method of exposing an optical disc master plate.
2. Discussion of the Background Art
According to a document, entitled xe2x80x9cDVD Specifications for Recordable Disc/part 1. Physical Specification Version 0.9 April 1997xe2x80x9d, the DVD-R disc format forms a wobble track recorded with a sinusoidal wave signal of constant frequency for use in the synchronization of disc rotation and a land pre-pit for storing address information, etc., over the entire information area. The land pre-pit is the pit disposed on the land between the wobble tracks, and is formed in constant relationship with the wobble phase of the track. FIG. 13 is a graph showing the phase relationship between the wobble signal and the pre-pit signal.
As shown in FIG. 14, the land pre-pit employs a 2-sync.-frame length as one unit and sets an even number position and an odd number position at the head portion each of the 1-sync.-frame lengths. The length of 1-sync.-frame equals the length of an 8-wobble period. An overlap between the tracks on which the land pre-pits are formed adjacently to each other can be avoided by changing the position thereof, so that the land pre-pit is successively formed on a spiral track. If the land pre-pits overlap each other, the land pre-pit signal cannot be correctly reproduced at the time of DVD-R (format) reproduction. However, in regard to the exposing apparatus of the optical disc master plate for exposing the photoresist master plate and writing in the DVD-R format, it is not well known in the related technology that the wobble signal for wobbling the track output from the exposure signal generating apparatus (formatter) which generates the exposure signal for exposing the photoresist master plate is precisely synchronized with the land pre-pit signal.
In regard to the formatter, it can be understood that the wobble signal is generated by the wobble signal generating apparatus, the land pre-pit signal is generated by the land pre-pit signal generating apparatus, a certain phase point during the wobble period of the wobble signal is extracted, a trigger signal is created in order to output the land pre-pit signal in a certain phase relationship with the wobble signal based upon the phase extracting signal, and the trigger signal thus created is output to the land pre-pit signal generating apparatus.
However, in such a formatter as mentioned above, a variation width occurs at the extracted phase point. This variation width is also superposed on the trigger signal. As a result, the precise land pre-pit signal cannot be output.
The present invention was made in consideration of the above-mentioned and other problems in order to improve such various subject matters.
It is an object of the present invention to solve and improve the above-mentioned and other subject matters on the defects of the related background arts.
It is another object of the present invention to provide a novel apparatus for exposing an optical disc master plate capable of solving the defects of the related art and a method of exposing an optical disc master plate.
It is still another object of the present invention to provide a novel exposure apparatus for exposing an optical disc master plate capable of precisely synchronizing a wobble signal with a land pre-pit signal in an exposure signal generating apparatus and outputting therefrom the synchronized signals.
It is still another object of the present invention to provide a novel exposure apparatus for exposing an optical disc master plate which enables an exposure signal generating apparatus to facilitate the design of a separation element for electrically separating an analog circuit and a digital circuit from each other and a circumferential circuit thereof
It is still another object of the present invention to provide a novel exposure apparatus for exposing an optical disc master plate which simplifies the adjustment of the track wobble phase and the land pre-pit forming phase.
It is still another object of the present invention to provide a novel exposure apparatus for exposing an optical disc master plate capable of avoiding an overlap of the land pre-pits upon on each other without the addition of a special circuit, etc. to the exposure apparatus.
It is still another object of the present invention to provide a novel exposure apparatus for exposing an optical disc master plate capable of judging in advance the occurrence of an overlap between the land pre-pits for each revolution of the photoresist master plate and avoiding the occurrence of the overlap therebetween.
It is still another object of the present invention to provide a novel exposure apparatus for exposing an optical disc master plate further capable of precisely avoiding the occurrence of an overlap between the land pre-pits on such an occasion.
It is still another object of the present invention to provide a novel exposure apparatus for exposing an optical disc master plate capable of avoiding the occurrence of an overlap between the land pre-pits with high resolution and high accuracy.
It is still another object of the present invention to provide a novel exposure apparatus for exposing an optical disc master plate capable of reducing the burden of the processing operational calculations for avoiding an overlap between the land pre-pits.
It is still another object of the present invention to provide a novel exposure apparatus for exposing an optical disc master plate capable of compensating for any variation of the rotative speed of a photoresist master plate which occurs due to an environmental change, etc. and precisely avoiding an overlap between the land pre-pits.
It is still another object of the present invention to provide a novel exposure apparatus for exposing an optical disc master plate capable of providing an alarm signal for indicating the presence of an abnormal state in avoiding an overlap between the land pre-pits and for avoiding an abnormal state in the (straight) line velocity of the exposure.